The Related Applications referenced above describe a network of wireless sensor nodes, referred to as wireless integrated network sensors (WINS). These nodes include communications, signal processing, data storage, and sensing capabilities, and the ability to autonomously form networks and perform cooperative signal processing tasks. These processing tasks include, for example, cooperative acoustic or seismic beam forming to locate targets or other nodes. This information can then, for example, control a camera to train upon the indicated location, if associated identification algorithms indicate that the target is of an interesting class. Human operators can be involved in the identification if information is conveyed from the sensor network. For example, the images and sensor data may be displayed using standard browsing tools, and commands sent to re-prioritize the activities of the remote network.
The seismic and acoustic location techniques can be vulnerable to a variety of environmental factors, and thus can have limited accuracy in some deployment circumstances. For example, non-homogeneity of the terrain results in multipath propagation and variable propagation speeds, while wind and certain thermal conditions can affect the usefulness of acoustic ranging systems. Such systems can also have difficulty separating targets that are in close proximity. These deficiencies can, to some extent, be ameliorated using a sufficiently dense network of sensors, but the signal processing tasks can then become very complicated. Moreover, it may demand energy-intensive communication of large quantities of data for coherent processing.
By contrast, if a line of sight exists between a node and a target, laser tracking systems like those described in U.S. Pat. No. 4,063,819, for example, are highly selective among targets and insensitive to most environmental conditions on the ground except extreme fog. Numerous commercial realizations of the laser tracking systems exist in compact form factors, such as for example the AN/PAQ-1 compact laser designator. On the other hand, constant scanning by active lasers is power intensive because of the laser and the associated servo mechanisms, and the requirements for large amounts of power can be problematic in compact self-sufficient node packages.
In the drawings, the same reference numbers identify identical or substantially similar elements or acts. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced (e.g., element 104 is first introduced and discussed with respect to FIG. 1).
The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.